If the guy down the street rides a horse to work when everyone else drives a car, it’s fair to assume he’s doing it deliberately.

Likewise the many U.S. senators who persist in filing their campaign finance reports only on paper and not online. Paper isn’t the slowest possible way to disclose political money; clay tablets would in fact be slower. But you don’t have to be a cynic to wonder why the U.S. Senate seems allergic to 21st century information technology.

Not to get personal, but Washington’s two senators, Democrats Patty Murray and Maria Cantwell, aren’t among the 20 senators who voluntarily file electronically. For both of them, this would be an excellent year to start.

In contrast, members of the U.S. House of Representatives, state legislators and countless other elected officials e-file their donation reports directly to disclosure agencies. Voters can then spot the donors shortly after the money arrives in candidates’ war chests.

The U.S. Senate prefers a more gentlemanly pace. It requires that printed reports be dropped off at the office of the chamber’s secretary. The Federal Election Commission collects the documents, copies them and delivers them to a private company in Virginia, where employees enter the information by hand, a keystroke at a time, into computers, and return them to the FEC. At last, the dollars and donors show up in a searchable database.

The whole laborious process can take weeks. A candidate could get a big dump of cash from Big Tobacco 10 days before the election, and voters might not find out until the folks at Philip Morris are toasting his victory.

Michael McAuliff, a political analyst at the Huffington Post, summed up the benefits for incumbent senators:

“The practice effectively gives Senate campaigns more time in which to portray the filings the way they want to before anyone else can verify them. It often reduces coverage of the reports when they are eventually filed, because they seem like old news by the time they are available.”

That may explain why the Senate hierarchy — including Majority Leader Harry Reid — has shown so little interest in change.

Sen. Jon Tester, a Montana Democrat, has sponsored a bill that would require e-filing. It has accumulated 37 co-sponsors from both parties, but Reid has never brought it up for a floor vote. (The lack of interest is bipartisan: Like Reid, Senate Republican leader Mitch McConnell doesn’t e-file.)

Tester’s bill seems likely to pass by the end of the century. In the meantime, nothing prevents any senator from voluntarily using the Senate’s electronic filing system. Murray and Cantwell, whose constituents include such tech giants as Microsoft and Amazon, shouldn’t find it excessively difficult.

The Olympian and other McClatchy newspapers in Washington state are jointly publishing this editorial as part of Sunshine Week, an open government project led by the American Society of News Editors.